Over the years a number of systems have been developed and installed for selectively controlling the entry into a locked building, e.g., apartment houses, through the use of telephones located in a number of rooms along with an auxiliary control and switching units for communicating with individuals seeking entry and for controlling the release of the lock.
Several of these systems, such as disclosed in U.S. Pat. No. 3,917,911 issued Nov. 4, 1975 to J. M. Lesher, U.S. Pat. No. 3,947,641 issued Mar. 30, 1976 to A. E. Trell and U.S. Pat. No. 4,113,986 issued Sept. 12, 1978 to G. F. Clement et al., use commercial telephone central offices to establish selective communication and control paths between tenants and a visitor seeking entry through a single locked door.
Other systems have been developed for selectively controlling access through a number of locked gates. One such system known as the Affirm Facility Management Systems manufactured by the Western Electric Company, Incorporated, New York, N.Y., utilizes an on-line card to limit entry by person, building, time of day and day of week. To gain admission, an encoded identification cards is inserted in a card reader at a particular one of a number of entrances to a building. The reader scans the card and transmits the data to a local control unit which determines whether the card holder should be admitted through that entrance, at that time and on that day. The data base for these control functions stores several thousands admittance data and can be readily updated.
There is still a need for a rather simple security system for selectively releasing locked devices for facilities at a number of remote locations under the control of an operator stationed at a central office. In a system of this type, the controller operator executes the necessary control functions through the agency of a conventional telephone network. In such a system the control should be attained by pushbutton dialing a sequence of multifrequency call number signals which are utilized to effectuate the selective release of the locked facility to which a person is seeking entry. This system should also include the capability of limiting the time that the locked device is released so that the person must enter the facility during this time, otherwise the controls revert to an original condition. In addition, such a system should also place a limit on the time available for the controller to dial the distinct number sequence indicative of a particular location to which the person is seeking entry.